A long wait.

Are you crazy? Very few cars today come without air conditioning from the factory, and to add it later is a major operation. I once watched a coworker do that to a van in the '90s, and it took him almost two weeks to get it to work right. The sales people were told to never agree to do that again.

When you add AC after the fact you get a car with a chopped up firewall to make room for the extra hoses and wires, and you get a car that blows cold air. When you get a car that came from the factory with the AC built in, you get a properly formed firewall, larger generator to handle the extra electrical demand, heavier front springs to handle the extra vehicle weight, more insulation is built into the firewall, and a larger radiator to remove the excess heat that the condenser dumps onto it. Extra weight makes the car harder to stop so they used to come with larger brakes. Your car may already have those because so very few cars are built without air conditioning, it would be pointless to design a lighter-duty brake system for those few cars. Handling and ride quality will not feel normal unless the heavier springs are installed. That will require a four-wheel alignment. The Engine Computer, and Body Computer will need to have new software installed to accept the air conditioning system. Each one can take over an hour just for that. You'll need a different HVAC computer and the software will have to be installed for that too. They might have to add a second radiator fan and install new wiring harnesses. The compressor needs to be fitted to the engine where there are no brackets for it now. A new drive belt will be needed.

Do not even think this is going to get done in a week unless they have three or four people tripping over each other to work on it at the same time. GM dealerships are real busy already with all their other problems so there will likely be just one person working on your car in between taking care of other customers' urgent needs. They will be basically rebuilding the entire front half of the car. During the procedure it will likely spend some time in the body shop being repainted in the areas they had to cut. I wouldn't pester them until the end of the second week, and when it's done, they would sure appreciate a big bag of chocolate chip cookies.